Giant and Helical Exciton Dipole from Berry Curvature in Flat Chern Bands
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| Format: | Preprint |
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2026
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| _version_ | 1866911591922925568 |
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| author | Yang, Kaijie Zheng, Huiyuan Xu, Xiaodong Xiao, Di Cao, Ting |
| author_facet | Yang, Kaijie Zheng, Huiyuan Xu, Xiaodong Xiao, Di Cao, Ting |
| contents | We show that excitons forming between moiré flat Chern bands possess a substantial electric dipole moment comparable to the moiré lattice parameter times the elementary charge ($\sim10^2$ Debye). At a hole filling factor of one in twisted MoTe$_2$, the dipole moment of the lowest-energy exciton branch develops in-plane helical texture in momentum space from the intrinsic Berry curvature of electron and hole. By solving the Bethe-Salpeter equations, we demonstrate that an out-of-plane displacement field induces a Frenkel-to-Wannier exciton transition, accompanied by a reversal of the dipole texture helicity. The resulting attractive exciton dipole-dipole interactions lead to quadrupolar biexcitons that can be probed via two-photon spectroscopy. Our findings establish band topology as a tunable knob to engineer exciton dipole moments and pave the way to manipulate many-body interactions in the terahertz regime. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_12295 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Giant and Helical Exciton Dipole from Berry Curvature in Flat Chern Bands Yang, Kaijie Zheng, Huiyuan Xu, Xiaodong Xiao, Di Cao, Ting Mesoscale and Nanoscale Physics We show that excitons forming between moiré flat Chern bands possess a substantial electric dipole moment comparable to the moiré lattice parameter times the elementary charge ($\sim10^2$ Debye). At a hole filling factor of one in twisted MoTe$_2$, the dipole moment of the lowest-energy exciton branch develops in-plane helical texture in momentum space from the intrinsic Berry curvature of electron and hole. By solving the Bethe-Salpeter equations, we demonstrate that an out-of-plane displacement field induces a Frenkel-to-Wannier exciton transition, accompanied by a reversal of the dipole texture helicity. The resulting attractive exciton dipole-dipole interactions lead to quadrupolar biexcitons that can be probed via two-photon spectroscopy. Our findings establish band topology as a tunable knob to engineer exciton dipole moments and pave the way to manipulate many-body interactions in the terahertz regime. |
| title | Giant and Helical Exciton Dipole from Berry Curvature in Flat Chern Bands |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2604.12295 |